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Publisher Summary This chapter outlines the optical and mechanical properties of infrared laser window materials. Windows developed for high-power infrared lasers must have extremely small losses so that laser heating of the window do not optically distort the laser beam or thermally fracture the window. Polycrystalline material has been prepared using conventional hot-forging techniques. In addition, polycrystalline fluoride windows have been prepared using a fusion-casting technique. In this method, a two-zone vacuum furnace is used to first purify and then to grow, by unidirectional solidification, windows as large as 25 cm in diameter. The growth process must be carried out very slowly to prevent cracking because the thermal-expansion coefficient is large for these materials. Zinc selenide holds great promise as a window material because of its many favorable mechanical properties and its broad transmission range from 0.5 μm to beyond 18 μm. It is found that the chemical vapor deposition process lends itself well to the fabrication of irregularly shaped optics, even though uniformity of temperature and growth rates would not be trivial problems for large areas or convoluted shapes. |
